This is a question where we will mostly likely never get a proper answer on.
the publishers no longer liked cage of eden so the author was forced
to rush everything. Therefore leaving a bunch a plot holes and having
to come up with a conclusion as fast as possible. source
It probably has a rushed ending because the manga may have lost the
required ranking to keep being published, which means they more than
likely only gave for a few more releases to wrap the series up. source
Due to not making enough sales the manga has had a rushed ending forcing the writer to close it up as soon as posible. There for leaving indeed a bunch of plot holes and unused potentionals such as hades.